The present invention relates to a flying spot scanning system for communicating video information to a scanned medium, and more particularly to a system for activating a laser for a scanning system comprising a rotating polyhedron mirror for controlling a scanning laser beam.
Recently, improved recording devices, the so-called "laser printers" have been gaining popularity and have been meeting with commercial success. The major performance of "laser printers" is that visual data such as letters and pictures etc. derived from a computer, a word processor, and a facsimile device etc. are imparted to a scanned medium in the form of an electrostatic charge pattern. A laser beam functions as scanning light.
An example of the "laser printers" is disclosed in Starkweather, U.S. Pat. No. 4,034,408 issued July 5, 1977, entitled "Flying Spot Scanner".
The conventional laser printer requires a collimator lens, a beam expander lens and an f-.theta. characteristics imaging lens, (f: focal length .theta.: inclination angle) which are very costly thereby making the laser printer expensive and impractical.
Conventionally, the f-.theta. characteristics imaging lens is required to compensate for distortion aberration which is due to speedy beam scanning at the ends of the scanned medium. The f-.theta. characteristics imaging lens provides strong barrel aberration. With the help of the f-.theta. characteristics imaging lens, the laser beam scans on the scanned medium at a constant speed.
Thus, it is desired to develop laser printers at a practical cost. U.S. patent application Ser. No. 352,151 was filed by T. Tagawa et al on Feb. 25, 1982, entitled "FLYING SPOT SCANNER FOR LASER PRINTER", now U.S. Pat. No. 4,435,733, to propose a laser printer free of the f-.theta. characteristics imaging lens. This application is now U.S. Pat. No. 4,435,733, issued Mar. 6, 1984.
The laser printer of the present invention can be combined with the laser printer as disclosed in U.S. Pat. No. 4,435,733. The disclosure of that patent is further incorporated herein by reference.